Display devices are used in a variety of applications. For example, thin film transistor liquid crystal displays (TFT-LCD) are used in notebook computers, flat panel desktop monitors, LCD televisions, and Internet and communication devices, to name only a few. Some display devices such as TFT-LCD panels and organic light-emitting diode (OLED) panels are made out of flat glass sheets. With many display devices, the glass used in the panels must be flat to within approximately 150 and approximately 250 micrometers over the surface of the glass. Any warping or ripple in the glass will have deleterious effects on the display quality.
For purposes of illustration, in many display devices, such as those referenced above, it is useful to incorporate electronic components onto the glass substrate used in the display device. Often, the electronic components are complementary metal oxide semiconductor (CMOS) devices including TFT's. In these applications, it is beneficial to form the semiconductor structure directly on the glass material of the display.
Thus, many LCD displays often comprise a glass substrate with the transistors formed over the glass substrate, and beneath a layer of LC material. The transistors are arranged in a patterned array, and are driven by peripheral circuitry to provide to switch on desired voltages to orient the molecules of the LC material in the desired manner. The transistors are essential components of the picture elements (pixels) of the display.
As can be readily appreciated, any variation in the flatness of the glass panel may result in a variation of the spacing of the transistors and the pixels. This can result in distortion in the display panel. As such, in LCD and other glass display applications, it is exceedingly beneficial to provide glass substrates that are within acceptable tolerances for flatness to avoid at least the problems of warped glass discussed above.
Known methods of fabricating glass panels with acceptable levels of warp or non-flatness require empirically adjusting the glass cooling rate. However, this is clearly an iterative process and results in unacceptable yields and ultimately unacceptable cost in the final product.
What is needed therefore is a method of forming substantially flat glass that overcomes at least the drawbacks referred to above.